Here is a simple way to dial in the idle current of your output tubes. In this example, I am setting a pair of 6V6 tubes on the Gibson BR-9 amplifier. You can use this method for any cathode biased amp, including Class A. See diagram in video. If you want a copy, let me know. Can send a .jpg via e-mail. I have a complete series on Patreon covering repair of the Gibson model BR-9. Plus many other great tech tips. Take a look. https://www.patreon.com/dlab_electronics